UV radiation sensing has various applications in diverse fields, such as health monitoring and healthcare, forensic sciences, security and authentication, environmental hazard detection and/or purification, antique evaluation and restoration etc. In imaging applications UV wavelengths let surface artifacts appear in greater clarity, and allow visualization of smaller features than those which can be seen using visible light. In case of health monitoring and care, it is well known that while a moderate amount of UV exposure is beneficial, as UV radiation helps in production of vitamin D, melanin etc., overexposure to UV radiation can potentially cause health problems, starting from erythema (redness of skin, indicating skin damage) to severe health hazards, such as skin cancer, genetic mutations etc. Medical data shows that skin cancer caused by UV from sunlight is one of the most prevalent forms of cancer in the United States and worldwide. Therefore, there is a clear need for UV exposure meters.
Various commercial UV sensors are available currently. A popular form of UV exposure meter comprises sensors mounted on wearable accessories, such as wrist/arm bands, watches, belts, jewelry, clothing etc. UV sensors may comprise photodiodes, photocathodes, and/or photomultipliers. Each sensor may measure a portion of the UV spectrum such as UVA, UVB, or UVC, or some combination of them. Sensor readings from multiple sensors may be fused to mimic the erythema action curve, or detect when they are greater than the minimum erythema dose. The UV sensor may have a Teflon diffuser to emulate the ideal cosine response expected when human skin is exposed to UV radiation at various angles of incidence. Some examples of these sensor configurations can be found in an article, titled, “Sundroid: Solar Radiation Awareness with Smartphones,” by Fahrni et al., presented in UbiComp, 2011 conference, which is incorporated herein by reference. Smartphone/mobile device accessories, such as, add-on device jackets with UV sensors, have also been introduced recently. These accessories communicate UV measurement data to mobile devices like smartphones, tablets, notebooks, laptops etc. for further processing of data, displaying the results to the user, and/or receiving user input or input from other devices.
The state-of-the-art UV sensors are typically not integrated well into the internal circuitry of the mobile devices like smartphones, tablets etc. However, there are smartphone/tablet applications (“apps”) providing access to wide-area UV data maintained by government organizations (such as the Environmental Protection Agency (EPA)). These data are obtained from large scale fixed UV sensors deployed for agricultural sector and/or weather prediction which may also be broadcast via public media. While this solution is useful, it has certain drawbacks. Because the sensors are non-local, if the user is unable to access the internet, data related to personal safety (such as data indicating UV overexposure) will not be accessible. This is a fundamental limitation of non-local sensors. Furthermore, it is difficult to have real-time, accurate local UV measurement data with non-local sensors. In other words, as information is not local in nature, and specifically does not relate to the user of the mobile device, any “alert” that is generated would have to be generic and may not relate to the actual UV radiation user is exposed to.
As mobile devices like smartphones become the device of choice not just for communications and data consumption, but also for photography and health and fitness monitoring, it makes sense to integrate local sensors or cameras for detection of UV radiation into the mobile devices. Some existing references, such as U.S. Pat. No. 7,526,280, entitled “Service implementing method and apparatus based on an ultraviolet index in a mobile terminal,” focus on using smartphones for UV detection service, but do not provide any detail of how the mobile device physically integrates the sensing mechanism with other system components.